1. Technical Field
The present disclosure relates to a thermal electric power generator.
2. Description of the Related Art
As is well known to those skilled in the art, the rankine cycle is a theoretical cycle for steam turbines. The rankine cycle has been studied and developed for a long time. A waste heat power generator has also been studied and developed as described in Japanese Unexamined Patent Application Publication No. 2013-7370. The waste heat power generator recovers waste heat energy released from a facility such as a plant or a firing furnace to generate electric power.
In the waste heat power generator described in Japanese Unexamined Patent Application Publication No. 2013-7370, an evaporator recovers thermal energy from a waste heat medium, and the recovered thermal energy evaporates a working fluid in the rankine cycle. The evaporated working fluid activates a turbine electric generator. The working fluid that has activated the turbine electric generator is cooled and condensed by a water-cooling condenser. The condensed working fluid is sent to the evaporator again by a pump. This enables continuous generation of electric energy from the waste heat energy. In recent years, a waste heat power generator that can be set up not only in a large-scale facility, but also in a relatively small-scale facility has attracted attention.
The waste heat power generator is forced to be stopped in an emergency situation due to a malfunction in some cases. In such a case, a predetermined control is performed to safely stop electric generation of the waste heat power generator. Japanese Unexamined Patent Application Publication No. 2013-57264, for example, describes a technique for stopping operation of a power generator immediately after a flow of the working fluid is stopped. This prevents application of a reverse thrust force to an expander, for example.
As illustrated in FIG. 7, an electric generator 200 described in Japanese Unexamined Patent Application Publication No. 2013-57264 includes an on-off valve 215, a pressure equalization channel 217, an expander bypass channel 219, and a controller 220. The pressure equalization channel 217 extends so as to connect a portion of a circulation channel 206 which is positioned between the on-off valve 215 and the evaporator 202 and a portion of the circulation channel 206 which is positioned between a screw expander 203 and a condenser 204. The expander bypass channel 219 extends so as to connect a portion of the circulation channel 206 which is positioned between the on-off valve 215 and the screw expander 203 and the portion of the circulation channel 206 which is positioned between the screw expander 203 and the condenser 204. When the electric generator 200 is shut down, the controller 220 closes the on-off valve 215, and opens an expander bypass valve 218 and a pressure equalization valve 216 after operation of a working fluid pump 205 is stopped. When operation of the electric generator 200 is started, the controller 220 opens the on-off valve 215 and closes the expander bypass valve 218 and the pressure equalization valve 216 before operation of the working fluid pump 205 is started.
The technique described in Japanese Unexamined Patent Application Publication No. 2013-57264 is designed to recover heat from a heat medium having a relatively low temperature. A safe stop of the thermal electric power generator is required not only for the thermal electric power generator that recovers heat from a heat medium having a relatively low temperature, but also for a thermal electric power generator that recovers heat from a heat medium having a high temperature of 300° C. or more.